Placement Detection System

1. A placement detection system comprising: a placement table; an imaging device that images an object placed on the placement table through the placement table to generate an input image; and a control device that receives the input image, wherein the control device identifies a higher-level pixel having a pixel level higher than or equal to a predetermined pixel level in the input image, sets a threshold value of the higher-level pixel, sets a threshold value of a target pixel other than the higher-level pixel to a lower value than the threshold value of the higher-level pixel in accordance with a distance between the higher-level pixel and the target pixel, binarizes a pixel level of the target pixel in accordance with the threshold value of the target pixel to produce a binarized image, and detects a shape of the object by using the binarized image.

2. The placement detection system according to claim 1 , wherein the control device sets the threshold value of the target pixel as a linear function of the distance.

3. The placement detection system according to claim 1 , wherein the control device sets the threshold value of the target pixel as an exponential function of the distance.

4. The placement detection system according to claim 1 , wherein the pixel levels of the higher-level pixels of the input image range from 0 to 255.

5. The placement detection system according to claim 1 , wherein the control device identifies a different higher-level pixel having a pixel level higher than or equal to the predetermined pixel level, sets a threshold value of the different higher-level pixel, calculates an alternative threshold value in accordance with a distance between the different higher-level pixel and the target pixel, and sets a threshold value of the target pixel to the alternative threshold value if the alternative threshold value is larger than the set threshold value of the target pixel.

6. The placement detection system according to claim 1 , wherein the placement table is a transparent plate.